Optical fiber for optical amplifier

Details Optical fiber for optical amplifier Optical fiber for optical amplifier

2000-01-14

2002-11-12

Healy, Brian (Department: 2874)

Optical waveguides

Having particular optical characteristic modifying chemical...

C385S123000, C385S142000, C385S144000

Reexamination Certificate

active

06480663

ABSTRACT:

CLAIM OF PRIORITY
This application makes reference to, incorporates the same herein, and claims all benefits accruing under 35 U.S.C. §119 arising from an application for a Optical Fiber For Optical Amplifier earlier filed in the Korean Industrial Property Office on Jan. 20, 1999 and there duly assigned Serial No. 1647/1999.
1. Field of the Invention
The present invention relates to optical fibers for use in optical amplifiers, and more particularly, to an optical fiber for use in an optical amplifier, which contains dysprosium ion (Dy
3+
) and has an improved light amplification efficiency at a 1.31 &mgr;m band.
2. Description of the Related Art
In the manufacture of optical amplifiers used to amplify an optical signal having a wavelength of 1.31 &mgr;m which belongs to the zero dispersion wavelength of silica glass, rare earth elements, for example, neodymium (Nd), praseodymium (Pr) or dysprosium (Dy) in the form of ions, are commonly implanted into a glass base. However, in the case of doping the glass with Nd
3+
, fluorescence is emitted at a wavelength of 1.31 &mgr;m, which is considerably far from the zero dispersion wavelength, during the transition of
4
F
3/2
→
4
/
13/2
of Nd
3+
. The intensity of fluorescence emitted at the
4
F
3/2
level is very weak at a wavelength of 1.31 &mgr;m, compared to at other wavelengths, for example, at 890 nm and 1064 nm. Also, due to excited state absorption at the
4
F
3/2
level, optical gain decreases at a wavelength shorter than 1.36 &mgr;m. To account for these problems, a fluoride-rich glass has been suggested as a base material, instead of the silica glass. However, the use of the fluoride-rich glass fails to increase the optical gain to a desired level at the wavelength of 1.31 &mgr;m.
Also, Pr
3+
, as a rare earth element implanted into a glass in optical fiber manufacture, permits the utilization of fluorescence emission by the transition of
1
G
4
→
3
H
5
. Such a transition is more likely to occur than at other energy levels, and thus a high optical amplification efficiency is expected when Pr
3+
is used as a doping material.
However, the energy difference between the
1
G
4
and
3
F
5
levels is very small at3000 cm
−1
, and thus in using an oxide glass having a high lattice vibration energy of 800 cm
−1
as a base material, there is a high possibility of nonradiative transition occurring by Pr
3+
excited to the
1
G
4
level due to it multiple lattice vibration relaxation. As a result, the light amplification efficiency decreases rather than increases. Thus, in using Pr
3+
for the purpose of increasing the optical amplification efficiency in the manufacture of optical amplifiers, a base material having a low lattice vibration energy should be accompanied with Pr
3+
.
A fluoride glass containing ZrF
4
is widely known as a base material having a low lattice vibration energy. However, such fluoride glass has a low quantum efficiency at 4% or less, and thus it is difficult to obtain satisfactory performance in view of fluorescence lifetime. For this reason, research into use of a sulfide glass which has a lower lattice vibration energy than a fluoride glass, as a base material, has actively conducted.
U.S. Pat. No. 5,321,708 for an Optical Fiber Amplifier Doped With Dysprosium Ion For The 1.3 &mgr;m Wavelength Band to Tohmon et al and U.S. Pat. No. 5,694,500 for an Optical Amplifier Operating at 1.3 Microns Useful For Telecommunications And Based On Dysprosium-Doped Metal Chloride Host Materials to Page et al disclose the use of trivalent Dysprosium ions as a dopant for amplification of 1.31 &mgr;m wavelengths in optical amplifiers. However, I have not seen the use of dysprosium ions as a dopant for germanium-gallium-sulfide glass or for germanium-gallium-arsenic-sulfide glass.
SUMMARY OF THE INVENTION
An object of the present invention is to provide an optical fiber for use in optical amplifiers, which contains dysprosium ions (Dy
3+
) and has an improved light amplification efficiency at a wavelength of 1.31 &mgr;m.
The object of the present invention is achieved by an optical fiber for an optical amplifier, comprising a germanium-gallium-sulfide (Ge—Ga—S) glass, an alkali metal halide, and dysprosium (Dy) as a rare earth element.
Preferably, the content of alkali metal halide is in the range of approximately 1 to 20 mol % based on the total amount of Ge—Ga—S glass and alkali metal halide, and the content of rare earth element is in the range of 0.01 to 0.1 at % based on the total amount of Ge—Ga—S glass, alkali metal halide and rare earth element. Preferably, the alkali metal halide is KBr, CsBr, KI or CsI.
When KBr or CsBr is used as the alkali metal halide, an improvement of fluorescence lifetime at the 1.31 &mgr;m band is excellent regardless of the content of alkali metal halide. It is more preferable that the alkali metal halide content is greater than or equal to the Ga content, in view of the improvement of fluorescence lifetime.
When the alkali metal halide is KI or CsI, it is preferable that the Ga content in the Ge—Ga—S glass is 10 at % or more based on the total composition of the glass, for more improvement of the fluorescence lifetime at the 1.31 &mgr;m band. It is more preferable that the alkali metal halide content is greater than or equal to the Ga content, in view of the fluorescence lifetime increase at the 1.31 &mgr;m band.
It The object of the present invention is achieved by an optical fiber for an optical amplifier, comprising a germanium-gallium-arsenic-sulfide (Ge—Ga—As—S) glass, an alkali metal halide, and dysprosium (Dy) as a rare earth element.
Preferably, the content of alkali metal halide is in the range of approximately 1 to 20 mol % based on the total amount of Ge—Ga—As—S glass and alkali metal halide, and the content of rare earth element is in the range of approximately 0.01 to 0.1 mol % based on the total amount of Ge—Ga—As—S glass, alkali metal halide and rare earth element.


REFERENCES:
patent: 5321708 (1994-06-01), Tohmon et al.
patent: 5379149 (1995-01-01), Snitzer et al.
patent: 5694500 (1997-12-01), Page et al.
patent: 5973824 (1999-10-01), Sanghera et al.
patent: 6148125 (2000-11-01), Heo et al.
patent: WO97/03028 (1997-01-01), None
Communication (No. EP00300313.4) issued by the European Patent Office dated Oct. 31, 2001.
Doc. No. XP002180544, dated Feb. 1999, USA.
Doc. No. XP002042717, dated, 1996, NLX.

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